The following relates generally to wireless communication, and more specifically to semi-persistent scheduling (SPS) for shared spectrum.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Certain wireless communication systems may operate in a shared or unlicensed radio frequency spectrum band (e.g., in a MulteFire network) that base stations and/or UE may use without a licensed frequency anchor carrier. Access to the medium for wireless communications in a shared or unlicensed radio frequency spectrum band, however, is not guaranteed. Instead, wireless devices attempting to access the channel for wireless communications may perform a contention based process (e.g., a clear channel assessment (CCA) procedure, a listen-before-talk (LBT) procedure, and the like) to capture the channel. When successful, these contention based processes may permit the wireless devices to transmit on the channel during dynamically determined transmission opportunities (TxOPs). When unsuccessful, the wireless devices may perform a backoff procedure and may further attempt to communicate on the channel at a later time.
Wireless communication systems operating in a licensed radio frequency spectrum band may utilize semi-persistent scheduling (SPS) techniques. Broadly, SPS addresses a scenario in which a UE is expected to periodically transmit or receive data consistently over a time period. One example may involve voice calls over cellular, or other processes involving small packet transmissions with predictable payload over the time period. One advantage of SPS is a reduction of control signaling overhead. Conventional systems, however, have not adapted SPS techniques for use in a shared or unlicensed radio frequency spectrum where channel access is not guaranteed.